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Old Jan 26th 2018, 08:40 PM   #41
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Originally Posted by yafimski View Post
Sorry to ask these simple questions again but I'm not sure what to do.

I have the 'coil 1' I mentioned in the above posts. It's a tiny solenoid with DC12V on it.

I tried to attach the coil to the +/- of the battery and just bring it close to the magnet but it didn't differ from my previous trial - meaning the magnet just doesn't seem to be affected by the coil's magnetic field.

The battery I used is still the 9v.
Should I split an old laptop charge's cable and connect it to the wall?

Ahh ... only just seen this post .... the problem is this 9V battery ,it will do nothing ....

If you have an unwanted laptop power supply this can be useful .... this consists of a black box perhaps 15 x 5 x 3 cm ... one wire goes to the mains socket (power in) .... another wire coming out, plugs into the laptop and is DC voltage out , perhaps 19 V .... with the power supply disconnected from the mains cut off the plug that normally goes into the laptop . This will allow you to access the two wires that deliver the output voltage , connecting them to your coil should get some results , check the output voltage first, if bigger than the coil recommended voltage you may want to put some resistance in series , check the current with your meter in series (10A setting).

Last edited by oz93666; Jan 26th 2018 at 09:44 PM.
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Old Jan 30th 2018, 06:12 AM   #42
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Safely does it.

The problem is not with the voltage, it is with the amperage.
Most 9V batteries are designed for powering small transistor circuits, which require a low amperage.

If you join batteries in series you will get higher voltage, but the same amps
If you Join Batteries in parallel, you can draw more amps, at the same voltage.

If you can get several 9V batteries, and join them in parallel, you might start to get enough "umph" out to properly drive your solenoid.

Alternatively start with batteries that are designed to deliver a higher amperage (at lower volts) like bicycle lamp batteries.

Remember linking 2 in series doubles the voltage,
linking 2 in parallel doubles the amperage (to a reasonable approximation).
so by linking 4 in a combination of serial and parallel you could double both the volts and amps.

by linking 8, or 16 or, etc...

Be careful if you start linking lots of batteries together,
it is safer than mucking around with mains driven transformers, but you can still get a nasty belt of a stack of batteries.

Last edited by Woody; Jan 30th 2018 at 06:16 AM.
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Old Jan 30th 2018, 10:08 AM   #43
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Do you think that parallel 9v should be better than a laptop charger...?

What is your recommendation?

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Old Jan 31st 2018, 03:02 AM   #44
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You want a lot of power in a short time,
A laptop charger is designed to give a trickle of power over a long time.

If one were to open a 9V battery
(not recommended, there are some moderately nasty chemicals inside)
you would find 6 little 1.5V batteries, arranged in series.
(The chemistry of batteries means that a single cell will give 1.5V,
these then need to be stacked to get higher voltages)

Note that the individual 1.5V cells in a 9V battery are quite small,
and so are individually only able to supply a small amount of power.

I would try taking lots of the larger style of 1.5V batteries
(the old fashioned type used for hot filament bulb bicycle lamps,
before high efficiency white LEDs were developed)
and arrange them in a grid, perhaps 5 or 6 long, by 3 or 4 wide.

6 stacked in series will give 9V,
3 of these stacks, linked in parallel will give 3 times the power of 1 stack.

Last edited by Woody; Jan 31st 2018 at 03:06 AM.
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